Shopsmith Forums

What jumps out at me is that your measured values look a lot like mine but from measuring the Idler, not the Main. Your stated motor speed (5480) is, I presume a typo? 3580 is more realistic. (Or is that the problem?) If I'm understanding your data correctly, your high and low speeds are even high compared to BuckeyeDennis earlier in the thread. I've thought about his numbers, 1055 and 6533, but don't have a theory.

- David

DLB wrote: ↑Thu Aug 11, 2022 4:04 pm What jumps out at me is that your measured values look a lot like mine but from measuring the Idler, not the Main. Your stated motor speed (5480) is, I presume a typo? 3580 is more realistic. (Or is that the problem?) If I'm understanding your data correctly, your high and low speeds are even high compared to BuckeyeDennis earlier in the thread. I've thought about his numbers, 1055 and 6533, but don't have a theory.

- David

3580 it is. I corrected my previous post.

You are also correct in that the measured speeds were those of the idler shaft.

Thanks for the corrections. I also found that my drive belt is not 27" as I had thought. It is actually 26 5/8" top measurement.

Thanks for keeping me honest. This whole thing is beginning to come together.

dusty wrote: ↑Thu Aug 11, 2022 6:01 pm 3580 it is. I corrected my previous post.

You are also correct in that the measured speeds were those of the idler shaft.

Thanks for the corrections. I also found that my drive belt is not 27" as I had thought. It is actually 26 5/8" top measurement.

Thanks for keeping me honest. This whole thing is beginning to come together.

Your numbers look very much like mine then. Generally within 10% of the table, with everything on the high side. My impression of mine is that I can do a tachometer assisted calibration of the indicator dial and move everything, or at least the speeds I use, to within 5%.

- David

I sure hope the OPs questions have been answered.

Hope this becomes as useful for others as it did for me.

It is an Excel spreadsheet that can be used to determine shaft speeds given different size sheaves , Included are the formulae for each of the cells in the spread sheet (very useful if you make an inappropriate entry into a cell); doing so could really alter the results.

When using this, I typically enter sheave size into E23 and then copy and paste into C3. Users Choice.

Change motor speed to whatever motor speed may be of interest and then center 1.9894321 into E23. This should give you shaft speeds for when the upper sheave and lower sheave are the "same size".

Thank you, DLB. Dave pointed out an error in the previous posted. The formula in C19 will most commonly be C18/1.6. Sorry about the confusion that that might have caused.

I have changed my spead sheet some and will post it here as well. Please understand that this was a toy developed to help me better understand the relationship if the sheaves when the size of the drive sheave (C8) is altered.
Another

Are the various dimensions of the sheaves "critical" to the operation of of the "speed control mechanism" of the Shopsmith. I have recently had access to six different sets of sheaves and I find that they vary significantly in size. These came from an individual who had been parting out, repairing and selling Mark 5's as assemblies and for parts. Thus the sheaves may be questionable samples.

What do y'all think?

I believe that they need to, as a minimum, being matching pairs!!

Question is, WHAT dimensions vary?

I think other than bore/fit etc., the slope of the bevel dimensions from the center axis is the only thing.

That said, as sloppy as a reeves drive is what does it matter?

Just about every dimension other than the bore - particularly the outer diameter and the length of the vanes and the angle of the slope..

The vanes should not come into play except for the control sheave, then their distance from the button bearing end matters(where the pork chop touches).

The od is minor since it only comes into play when the belt is OVER extended on the pulley.